In an effort to expedite ticketing and handling of passengers on the airlines, a magnetic tape is located on the back of ticket coupons. The magnetic tape extends for the length of the coupon and is encoded with all of the information printed on the front of the tape. For example, the ticket holder's name, destination, flight numbers, and dates are among the data printed thereon and encoded on the magnetic strip. To accurately encode the information on the magnetic strip and to accurately read the information thereon, it is necessary that the speed of the coupon moving past the reader/encoder be accurately controlled.
There are regulations governing the configuration of the ticket, location of the magnetic tape and other information on the ticket. So that tickets will be uniform throughout the world, the International Air Transport Association has issued a set of ticketing resolutions. Resolution 20.200 issued by the IATA requires that the velocity of the coupon passing the head is within plus or minus 8 percent of the specified velocity and preferably within plus or minus 4 percent of the specified velocity.
In an effort to comply with these requirements, the industry has had to resort to use of expensive, constant velocity, encoded direct current motors which, when used in the system, increase the cost of the system. Even though such systems are relatively expensive they barely control the velocity within the required specifications.
Even when constant velocity motors are used, it is necessary to provide means for tensioning the belt drive used in the system. One prior art system is illustrated in FIG. 1 and is generally designated by the reference character 10. The system 10 includes a constant velocity d.c. motor 12 which drives a toothed belt 14. The toothed belt 14 is looped over a primary coupon drive wheel 16 and a secondary drive wheel 18 and returns to the motor 12. In the system 10, there is provided a tensioner 20 having a cantilever arm 21 which, through a spring 22, exerts a force on the belt 14 to keep the belt tight, it is necessary to keep the belt tight to eliminate oscillation of the belt and velocity changes in the coupon feed speed that occur as a result.
Apparatus was set up to record the velocity variations of a sample ticket coupon 24 being run through the prior art system 10. The results of the velocity recording are shown in the graph of FIG. 5. As shown therein, the velocity of the coupon was in excess of plus or minus 8 percent initially and gradually dropped to a speed variation of within plus or minus 4 percent. It is possible that much of the initial speed variation is due to inertia of the belt tensioner 20.
One technical advantage of the present invention is that the tensioner includes a damping portion contained within the tensioner body so that the tensioner can be located on a fixed post or shaft. Also, the tensioner does not contain oscillating parts such as the cantilever arm and spring of the prior art systems. Thus, the tensioner itself does not contribute to the speed variation of the belt drive system.
Another technical advantage is that the tensioner, because of its location, assists in absorbing any speed variation that may be imparted due to eccentricities, belt flexure, etc. that may be imparted by other portions of the belt drive system.
A further technical advantage of the invention is that the tensioner can be utilized for driving auxiliary systems since it is mounted on a fixed post or shaft.